Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$191.46	13.628%	$217.5522	$217.55	$217.55	$217.60
Purchase #2	$147.69	7.821%	$159.2408	$159.24	$159.25	$159.20
Purchase #3	$188.60	13.371%	$213.8177	$213.82	$213.80	$213.80
Purchase #4	$191.74	13.235%	$217.1168	$217.12	$217.10	$217.10
Purchase #5	$52.45	10.270%	$57.8366	$57.84	$57.85	$57.80
Purchase #6	$35.97	11.568%	$40.131	$40.13	$40.15	$40.10
Purchase #7	$214.71	3.607%	$222.4546	$222.45	$222.45	$222.50
7 purchase totals =	$1,022.62		$1,128.1497	$1,128.15	$1,128.15	$1,128.10